System of power-refrigeration



Dec. 5, 1967 J. K. LA FLEUR SYSTEM OF POWER-REFRIGERATION Filed Jan. 4, 1965 2 Sheets-Sheet l INVENTOR. James I ZAJF'ZEUQ 4 ATTORNEY J. K. I A FLEUR Dec. 5, 1967 SYSTEM OF POWER-REFRIGERATION 2 Sheets-Sheet 2 Filed Jan. 4, 1965 .JINI

D NOICQMZMWN- OJOU R E0 LT FN Aw Lm y W J auf ATTOQNEV United States Patent O ABSTRACT F THE DISCLOSURE This invention is directed to a power-referigeration system, particularly design for the liquefaction of air, nitrogen and other gases of low boiling temperature, including a closed refrigeration cycle wherein a refrigerant gas such as helium is compressed, cooled, further compressed, regeneratively cooled, work expanded to low temperature, passed in heat exchange relation with a refrigeration load such as nitrogen for liquefying same, regeneratively heated and recompressed. In one embodiment, a portion of the further compressed refrigerant is additionally compressed, regeneratively cooled, work expanded for further reduction of temperature, passed in heat exchange relation with a second refrigeration load, regeneratively heated and recompressed. In another modification a hot power cycle is included, in which a portion of the compre-ssed refrigerant, e.g., helium, is heated, expanded in a hot power turbine, cooled and recompressed, such power turbine providing the main source of power for compression of the refrigerant in both the power cycle and the refrigeration cycle.

This invention relates to a closed power-refrigeration system employing a gas as the refrigerant medium, and is particularly concerned with an improved versatile powerrefrigeration system in which the expander for expansion and cooling of the refrigerant assists the main compressor, and employing means for this purpose which permits the expander to be located remote from the main compressor and in the immediate vicinity of the refrigeration load, thus increasing the efficiency of the system.

In my copending application Serial No. 318,564, now Patent Number 3,194,026, there is described and claimed a closed power-refrigeration system in which a gas is the common working medium in both a power cycle and a refrigeration cycle, that is, such cycles are interconnected so that the common working medium circulates between both cycles of the system. The system of said application comprises a closed gas turbine cycle having connected thereto a closed refrigeration cycle obtaining its motivation by diverting a portion of the common working medium from and returning such medium to the power cycle.

Thus, according to the process of said copending application, utilizing a very low boiling point gas such as helium as the common working medium, such medium is first compressed substantially and the compressed medium is then divided into a first stream and a second stream. The rst stream circulating in the power cycle is heated to raise the temperature substantially, and the so-heated iirst stre-am drives a so-called hot turbine which comprises the main portion of the power for the compressor. The expanded first stream of gas exiting the hot gas turbine isthen further cooled and returned to the compressor for recompression.

The above-noted second stream of compressed working medium, that is helium, circulating in the refrigeration cycle is cooled, and such cooled stream is used to drive a second or so-called cold turbine or expander. The expanded second stream of helium exiting the second turbine is now at a very low temperature, that is, a cryogenic temperature, and can function as a refrigerant by passing CII same in heat exchange relation with a medium to be ICC cooled, and the resulting or exiting second stream, after further heating thereof, is returned to said compressor for recompression.

According tothe above application the power output of the cold turbine or expander, as in the case of the hot turbine, can be coupled directly to the shaft of the compressor to provide a portion of the power required for compressing the helium therein, or the cold turbine can be coupled to a generator to provide electrical power for any desired use.

However, although under certain circumstances it is desirable to have the power output of the cold turbine or expander in such system directly assisting the hot turbine in the task of driving the compressor, it may be neither feasible nor desirable to have the cold turbine coupled directly to the shaft of the compressor. Some of these conditions are as follows:

(1) The case where the refrigerationload is located a great distance from the turbo-compressor. Location of the cold turbine and its loading device at the place where the refrigeration is required would eliminate long fluid transfer lines operating at low temperatures, and would eliminate the attendant refrigerant losses to the atmosphere.

(2) The case where it is desirable to operate the cold turbine at a different rotational speed than the main compressor unit.

(3) The case where more than one compressor assembly is desirable.

(4) The case where more than one refrigeration expander or turbine is desirable, as for example, where refrigeration is required at two different temperature levels.

One object of the invention accordingly is the provision of an improved closed cycle power-refrigeration system, and including the stages of compression of a gas refrigerant and expansion thereof, particularly for production of a low temperature gaseous refrigerant medium, and wherein such expansion of the refrigerant gas furnishes power which is utilized in the power-refrigeration cycle.

Another object is the provision of a power-refrigeration system including compression and expansion stages for a refrigerant gas, wherein the power from expansion of the refrigerant is employed directly in the system to increase the efficiency ofthe compression stage.

Stilla'nother object is the provision of a closed cycle power-refrigeration system of the type above-described in which the cold turbine or expander, and its loading device can be located adjacent the refrigeration load and at a distance from the compression stage.

Yet another object is the provision of a power-refrigeration system according to the above copending application, and including a closed hot power cycle and a closed refrigeration cycle interconnected with said power cycle, said cycles having a common compressor and employing a common working medium in both cycles, and incorporating means in the refrigeration cycle and driven by the power output of the cold turbine or expander in said cycle for assisting the hot turbine in the power cycle in the task of driving the common compressor.

Other objects and advantages of the invention will appear hereinafter.

The above objects are achieved according to the invention by incorporating an auxiliary or so-called boost compressor in the power-refrigeration cycle and using the cold turbine or expander in the refrigeration cycle to drive the boost compressor. Thus, the boost compressor is incorporated into the refrigeration cycle so as to accept the output of the main or primary compressor, and which in the system of my above copending application is driven by the hot turbine in the hot power cycle, and increases the pressure of the gas used as working iiuid in the refrigeration cycle of the system. The increase in refrigerant gas pressure accomplished by the boost compressor can vary and is generally moderate, ranging, for example, -from about to about.25%, or higher, .of the pressure `of the gas from the main compressor exhaust. In this manner, although the power output from the cold turbine is used for -such additional or incremental compression of the initially compressedworking medium, and thus assists such main compressor, the cold turbine or expander .isnot directly connected'or coupled to the main compressor lfor .thispurpose Hence the cold turbine can be locatedat any desired distance from the main compressor and, for example, can be located closely adjacent the refrigeration load. This means that the piping between the cold turbine andthe refrigeration-load vcan be made relatively short so thatessentially no loss of heat or refrigeration occurs even though the refrigeration load is located remotely from the compressor or hot power loop.

.The system of the invention has further advantages. Thus, several cold loops or cycles may be operated in parallel ,asdescribed in Amy copending application Serial No. 410,222, `tiled November 10, 1964, in an eflicient manner from a single supply line, in order tooperate several cold loops at different temperatures or .to operate several cold loops at different locations. -Further, although the auxiliary or .boost compressoronly adds a minorincrement of pressure to the pressure of the refrigerant produced by the main compressor, the incorporation-of such boost compressorin the refrigeration .cycle as .described above generally increases the efficiency of .the .system under the conditions of operation generally employed.

AThe principles of the invention can be applied basically to a system which contains but a single closed'loop, that is, a closed'refrigeration loop in which the'main compressor is driven, vfor example, by an electric motor ,or a gas turbine. Further, the 'invention principles can be applied to advantage in the cold loop of the system of my above copending application Serial No. 318,564, and including a hotpower loop in whichthe hot turbine drives the main vcompressor for furnishing the main source of power for the refrigeration cycle. An .important feature of such a system is that the coldlloop is a mirrorimage of thefhot power loop. That is, the cold turbine with ,its attendant boost compressor inthe refrigeration cycle ,is .constructed inthe same manner as the hotturbine 'and 'the primary compressor in thehot power cycle. This facilitateszmanu facture and assembly ofthe turbocompressor and turbine units for both the hot power cycleand'the cold refrigeration cycle, preferably employing units of the type Vdescribed and claimed in my copending applications 'Serial Nos. 273,910, now Patent Number 3,201,941, and A274,- 045, now Patent 'Number 3,202,341, bothled April 1'8, 1963, for this purpose.

The power-refrigeration system of vmyabove copending application Serial No. 318,564, and of the-present invention have application lfor the liquefa'ction vof -air, `nitrogen Vvand othergases such `as helium and'hydrogenhaving very low boiling temperatures, kand have particular'application for 'producing yrefrigeration for economically 'liquefying air according to the system of mycopending application Serial No. 273,883, now'Patent Number 3,258,929, L'iled April 18, f1963fThus, aparticularly importantfapplication of the invention system is for the flique'faction of 'air'and `air components such as nitrogen, employing vvery low boiling gases, e.g. those having a boiling vpoint lower than the boiling point of nitrogen, such as helium,hydrogen or neon, as the refrigerant 'working medium, land obtaining cryogenic refrigerant temperatures while maintaining the refrigerant in the gaseous state.

The invention will be more readily understood from the description below of'certain embodiments ofthe invention taken in connection with the-accompanying drawing wherein:

FIG. 1 is a schematic drawing or flow sheet of one embodiment of the invention;

FIG. 2 is a schematic representation of a preferred embodiment of the invention;

FIG. 3 is a schematic illustration of another modification of the invention; and

FIG. 4 illustrates a modified form of-the system shown in FIG. 3.

Referringto FIG. 1 of the drawing, in this embodiment the main compressor 1G is coupled at 14 to an electric drive motor 12. A 4gaseous refrigerant medium, eg., helium, is fed at approximately ambient temperature to the inlet 13 of the main compressor 1t), and the compressed helium exhausted from the compressor at 15 is passed through a coil 16 of an atmospheric cooler 17 to the inlet 18 of the boost compressor 2t).

The pressure of the helium gas is increasedin theboost ,compressor 20 and is exhausted therefrom andis passed through a coil 22 of the atmospheric cooler 17 to a cold regenerator 24. The compressed helium gas is kpassed through coil 23 of cold regenerator 24 in heat-.exchange relation with helium gas returning from the refrigeration load, as hereinafter described, and then is introduced into the inlet -side v26 of the expander or cold turbine 28. The cold turbine 28 is interconnected bya common shaft l29 .with the boost compressor 20 for driving -said compressor. The expanded and further cooled helium gas exiting `the .cold turbine at 30 is then passed through aIcoil 32 of the refrigeration load 34. Said coil 32 can be a coil in a Condenser for liquefying therein a gas such as nitrogen, or a coilin the top of an air separation or rectification column asfdescribed inrmy above copending application Serial No. 273,883. The helium which is heated by passage through the refrigeration load is conducted by a conduit36 to the cold regenerator 24 and passed therein through a coil 38 in heat exchange relation with the compressed helium gas `inicoilf23, forcooling same, and following'passage-ofthe heated'helium `through the cold regenerator 24 itis recirculated to the inlet -13 of the `main compressor as .noted above.

It .isaccordingly seen that the power derived :from the .cold turbine 28 is employed by boost compressor 20 `for .further compressing the initially compressed helium in the main compressor 1t), and hence cold turbine 28 assists the main compressor 1t) in its task of building .the rpressure-of the helium up to a greater pressure at-the intake vof the .expansion turbineZS. Hence, by meansofthe boost compressor 20, the power output of the cold l'turbine .28 .is employed directly in the powerrefrigeration loop without being coupled directlyto themain-compressor .10. This permits the cold turbine 28 and its loading boost compressor 20 to be located closely adjacent the refrigeration load 34 so that the conduit 30 connecting the cold turbine outlet with the refrigeration load .is relatively short, with substantially .no heat or refrigeration "losses resulting from passage of the cold expanded .refrigerant .from the exhaust of cold turbine 218 .to the -re frigeration load.

`FIG. V2 shows the application of the invention principles in the preferred system of my above .copending application Serial No. 318,564. As will be seen `the cold or refrigeration cycle, designated A in FIG. 2, isrthe same as that shown in FIG. 1 and the same part numbers are employed in FIG. 2 for corresponding parts in FIG. 1. lThe letter `B in FIG. 2 represents the hot power cycle o'f the system 4for supplying the power to the main compressor 10, in place of the electric motor 12 employed in FIG. 1.

Again, for `purposes of illustration and by way of example, the system of FIG. 2 will be described below as employing helium as the working gas medium for both the power and refrigeration cycles. The temperatures and pressures hereinafter are only by way of example, and all pressures are expressed in pounds per square inch absolute and 'temperatures are in degrees Rankine R.). As'- suming the whole system of power and refrigeration has been in operation for a sucient time to reach 'the Vin'- tended operating conditions of temperature and pressure, helium enters the compressor at a pressure of 181 p.s.i. and at ambient temperatures of 530, and the helium is discharged from the high pressure side of the compressor at 268 p.s.i. and 618. The flow from the compressor outlet is divided into two high pressure streams, namely a power stream which flows through branch 40 or the power loop, and the refrigeration stream which flows through branch 1S or the refrigeration loop. The high side of the powerstream, or the hot stream, first passes through one side of a regenerator 42 called the hot regenerator where the gas is heated to 1,493 at the outlet. From the regenerator 42 the power stream passes through the heat exchange coil 43 of a heater 44 which can be a combustion chamber and which serves to heat the helium to 1,660. Any suitable source of heat can be employed in the heater 44. The exiting power stream is then led to and used to drive a hot turbine 46 which provides the power for driving the compressor 10. The gas expands and cools in turbine 46, the pressure dropping to 190 p.s.i. and the temperature dropping to 1,498 and then passes through the other side, that is the low pressure side of the hot regenerator 42 wherein the gas is cooled while heating the high side power stream in countercurrent ow thereto to approximately the compressor discharge temperature. Finally, the gas passes through a precooler or sump 52 from which the gas is returned to the compressor 10. The precooler, either Water or air cooled, serves to bring the medium down to ambient temperature.

The cold or refrigeration stream of helium flowing from the exhaust of the compressor 10 at 15 then passes through the refrigeration cycle A in the manner described above with respect to FIG. l. Again, for purposes of illustration the helium which is cooled in the air chamber 17 or aftercooler, is cooled to 530, approximately ambient temperature, the pressure drop being slight, eg., about 5 p.s.i. In the boost compressor 20, the pressure of the helium gas is increased to about 300 p.s.i. and following passage of the further compressed helium through the cold regenerator 24, the helium is reduced to a temperature of about 141. The helium gas emerging from the regenerator 24 then expands in the cold turbine 28, the temperature of the helium dropping to 128. This is approximately the tempertaure of the helium refrigerant at the inlet to coil 32 of the refrigeration load 34. The medium to be cooled in the refrigeration load 34 may be a gas such as air to be liqueed, as previously noted, and its components separated as by rectilication. Such refrigerate gas is passed countercurrent to the flow of the helium refrigerant. The low pressure helium exiting the refrigeration load returns to the cold regenerator 24 where it serves to cool the compressed helium, and the helium then completes its refrigeration loop by returning to the compressor 10 at ambient temperature and compressor inlet pressure of 181 p.s.i.

In the embodiment of FIG. 3 `is shown a modification of the systems of FIGS. 1 and 2, employing a refrigeration cycle according to the invention, consisting of two separate cold loops. These separate cold loops are designated I and II in FIG. 3, of the drawing.

The cold loop I is the same as described above with respect to the embodiments of FIGS. 1 and 2. The second cold loop II is provided by diverting a portion of the compressed refrigerant, e.g., helium, following compression thereof in the first boost compressor 20 and cooling in cooler 17, through line 60 to a second boost compressor 62, thus further increasing the pressure of the helium gas so diverted. This further compresesd refrigerant gas is then passed through a coil 64 of a second cold regenerator 66 to further reduce the temperature of said compressed helium gas by passage thereof in countercurrent heat exchange relation with cold helium returning from the second refrigeration load 70, as described below. The further cooled and compressed helium exiting the cold regenerator 66 is passed to the intake of a second cold 6 turbine 68, causing expansion and a. further lowering of temperature ofthe helium from the exhaust of such turbine. The cold turbine 68 is coupled to the second boost compressor 62 for driving same.

The cooled expanded helium or refrigerant exiting the cold turbine 68 is passed via line 68 through a heat exchange coil 69 of a second refrigeration load 70 for cooling the refrigerate medium. After giving up heat to the refrigeration `load 70 the refrigerant gas now at a higher temperature is passed via line 71 through coil 72 of the cold regenerator 66 in countercurrent heat exchange relation with the compressed helium passing through coil 64 for coolinglsame as above noted. The further heated helium exiting the cold regenerator 66 is then conducted via line 74 into the line 36 which carries the refrigerant gas from the rst refrigeration load 32 to the first cold regenerator 24, for further heating of the returning he lium therein prior to return of all of the refrigerant to the intake of the main compressor 10. Both of the boost compressors 20 and 62 in the system of FIG. 3 operate at approximately the same temperature, e.g., near ambient temperature. Thus, in accordance with the modification of FIG. 3, two cold loops I and II are provided which can be operated at different locations.

In FIG. 4 there is shown a modification of the system of FIG. 3. In t-he modification of FIG. 4, the refrigerant for the second cold loop II is provided by diverting a portion of the compressed refrigerant, eg., helium, following cooling thereof in the cold regenerator 24. Hence the refrigerant temperature at the inlet to the second yboost compressor 62 in this modification is at a substantially lower temperature than that of the refrigerant` at the inlet to the first :boost compressor 20, and hence in this case the boost compressors 20 and 62 operate at substantially different temperatures.

Thus, in the modification of FIG. 4, it will be noted that as a result of the further compression of the helium in the second boost compressor 62 followed by passage thereof through the second cold regenerator 66 and the further expansion of the thus further compressed and cooled helium in the second cold turbine 68, the resulting refrigerant gas delivered to the second refrigeration load 70 is at a lower temperature than the refrigerant gas delivered from the exhaust of the first expander 28 t0 the first refrigeration load 34. Thus, in accordance with the modification of FIG. 4 there is provided two cold loops I and II supplying refrigerant gas at different temperatures vfor loads requiring different degrees of refrigeration, and further such two cold loops can be operated at different locations.

The principles of the invention in accordance with the modifications of FIGS. 3 and 4 can be applied particu- Iarly to the system described and claimed in my copending application Serial No. 410,222, noted above.

It will be understood that although theV modifications of FIGS. 3 and 4 show the principles of the invention as applied to the operation of two cold loops, the invention can be applied for provision of a system employing more than two cold loops in a closed refrigeration cycle, e.g., 3 or more such cold loops.

From the foregoing, it is seen that the invention provides a novel and improved power-refrigeration system comprising a closed cycle and including a main compressor, cooling means and an expander, and preferably employed in conjunction with an interconnected hot power cycle for actuation of the main compressor by means of a hot gas turbine, employing means in the form of a boost or auxiliary compressor in the refrigeration cycle `and driven by the mechanical energy derived from the expander, which increases the versatility of the system and improves its eiciency and which assist the driving means, e.g., the motor or gas turbine, in driving the main compressor.

While I have described particular embodiments of my invention for the purpose of illustration it should be understood...that various. modifications and adaptations thereofmaybe made withinthe spirit of theinvention, as

set forth in the appended ciaims.

. I claim:

1.l A power-refrigeration process which comprises compressinga gaseous Iefrigerant.cooling said compressed refrigerant, further compressing said refrigerant, `subjecting -saidso 4compressed refrigerant to regenerative cooling, expanding said further cooled refrigerant to accomplish work andfurther reducing the temperature of said refrigerant,.said work being employed for said tur- ,ther compression of saidrefrigerant, passing saidexpanded. and. cooled refrigerant to a refrigeration load to cool rsame, .employing the exciting refrigerant for said regenerating .cooling ofsaid compressed refrigerant, sub- ,.jecting a portion .of said further compressed refrigerant to additional compression, subjecting said additionally compressed refrigerant portion to regenerating cooling, expanding said 4cooled refrigerant portion to accomplish .work and further reducing the. temperatureV of said re- .frigerantportiom said work being employed for said ,additional compression of said refrigerant portion, passing said expanded and cooled refrigerant portion to a secv.ond refrigeration load `to cool same,1employing the exit- .ingrefrigerant'portion for said regenerative cooling of .said compressed refrigerant portion, and returning re- .frigerant heated in the above. regenerative cooling stages 'fonsaidffrstr mentioned compression, of said refrigerant.

.2. `A power-refrigeration process as dened in claim 1,

.wherein.saidrefrigerant .portion is diverted from the main .refrigerant stream prior .to said first mentioned regenerative cooling.

. 3. Apower-refrigeration process .asdefined inclaim 1, wherein said refrigerant portion is diverted from the main, refrigerant, stream subsequent to said first'mentioned regenerative cooling.

4. Apower-refrigeration process as `defined in claim 1, Whereinsaid refrigerant is helium.

.5. A power-refrigeration processas defined in claim 1, Whereinsaid refrigerantishelium. and wherein said relfrigeration` loadjn eachycase is nitrogen to be cooledrand liquefied.

L 6.A power-refrigeration processwhichcomprises heatinga compressed gas, .said compressed gas iiowing in a closed. power, loop, introducing said hot compressed gas intol a primemover andexpanding saidgas, cooling said gas andcompressing.,saidgas, the workv from.. said prime moverA being employed. .for .said last mentioned` compression, circulating a portion of said compressed gasfin said closed power ,loop` and. circulating .the remainder .of said compressedgashas refrgierantl in. a vclosed refrigeration ,loop whichA comprises vcoolingtsaid. compressed refrigerant; further` compressing said refrigerant,l subjecting said refrigerantheatedin .said regenerative cooling for said first, mentioned compression ofsaid refrigerant.

` 7. A power-.refrigeration .process which comprises heatingheliurn gas, said compressedy gas flowing in a closed .power loop, Aintroducingsaidhot compressed helium -gas intoa prime. mover and expandingsaid gas, cooling said helium andcompressingsaid helium, the work from said .primemover being employed fof said last mentioned cornpression,gcirculating a. portion ofsaid compressed helium gas in saidclosedA power loop. and .circulating the remainder of said compressed helium gas as refrigerant in a closed refrigeration loop whichcomprises cooling said compressed helium, further incrementally compressing saidcooled helium, subjecting said so-compressed helium to regenerative cooling, expanding said further cooled helium to accomplish work and further reducing the temperature of said helium gas to cryogenic temperatures, said work being employed for said further compression of said helium, passing said-expanded and cooled helium .to a refrigeration load to cool same,..employing the exiting helium for said regenerative cooling of said compressed refrigerant, and returning the helium heated in said regenerative cooling for said first mentioned compression of said helium.

8.*A power-refrigeration system which comprises a refrigeration cycley including, in combination, thecornponents consisting of a first compressor, a first cooler, a

.second boost compressor, a cold regenerator, an expander,

said expander being connected indriving relation with. said boost compressor, a .refrigeration load, first conduit means connecting the exhaust side of said first compressor .in seriatim with each of said components, andsecond conduits means communicating with said first conduit means ,and connecting said refrigerationload with the intake side of said first compressor and passing through said cold regenerator inV heat exchange relation therein with said first conduit means; a heater, a power turbine, third conduit means connecting the exhaust side of said first compressor and the intake side of said hot turbine and passing through said heater, asecond cooler, and fourth conduit means connecting the exhaust side of said power turbine and the intake side of said first compressor and .passing through said second cooler.

9. A power-refrigeration .system .which c includes, in combination, the components consisting of a -firstucompressor, means for driving said first compressor, a cooler, a second boost compressor, a first cold regenerator, a first expander, said expander being connected in driving relation with saidsecond boost compressor, afirst refrigeration load, first conduit means connecting the exhaust side of said rst compressor in seriatim with each of said=com ponents, and second conduit means communicating with said first conduit means and `connecting said `refrigeration load with the intake sideof said first compressor and passing through said cold regenerator in heat exchange relation therein with said firstf-conduitimeans, a third boost compressor, a second cold regenerator, a second expander, said second expander -being connected indriving relation with said third boost compressor, asecond refrigeration load, .third conduit means connectingI said first conduit means between said second boost compressor and said fir-st expander in seriatimwith said third boost compressor, said second cold regenerator, said second expander and said second refrigeration load, and fourth conduits means communicating -with said third conduit means and connectingsaid second refrigeration load withsaid second conduit means between said first refrigerationv load .and said'first cold regenerator, and passing through said second cold `regenerator in heat exchange therein-with said third conduit means.

References Cited UNITED STATES PATENTS 4244,236 7/1881 rHill 62-403 X 2,409,159 10/1946 Singleton 62-402 X 2,458,894 1/1949 Collins 62-40`X 2,909,903 10/1959 Zimmermann 62--40 X 3,144,3 16 8/1964 Koehn et al. 62-40 X 3,213,631 10/1965 Kniel 62-40 X NORMAN YUDKOFF, Primary Examiner.

vV. W. PRETKA, Assistant Examiner. 

1. POWER-REFRIGERATION PROCESS WHICH COMPRISES COMPRESSING A GASEOUS REFRIGERANT, COOLING OF SAID COMPRESSED REFRIGERANT, FURTHER COMPRESSING SAID REFRIGERANT, SUBJECTING SAID SO COMPRESSED REFRIGERANT TO REGENERATIVE COOLING, EXPANDING SAID FURTHER COOLED REFRIGERANT TO ACCOMPLISH WORK AND FURTHER REDUCING THE TEMPERATURE OF SAID REFRIGERANT, SAID WORK BEING EMPLOYED FOR SAID FURTHER COMPRESSION OF SAID REFRIGERANT, PASSING SAID EXPANDED AND COOLED REFRIGERANT TO A REFRIGERATION LOAD TO COOL SAME, EMPLOYING THE EXCITING REFRIGERANT FOR SAID REGENERATING COOLING OF SAID COMPRESSED REFRIGERANT, SUBJECTING A PORTION OF SAID FURTHER COMPRESSED REFRIGERANT TO ADDITIONAL COMPRESSION, SUBJECTING SAID ADDITIONALLY COMPRESSED REFRIGERANT PORTION OF REGENERATING COOLING, EXPANDING SAID COOLED REFRIGERANT PORTION TO ACCOMPLISH WORK AND FURTHER REDUCING THE TEMPERATURE OF SAID REFRIGERANT PORTION, SAID WORK BEING EMPLOYED FOR SAID ADDITIONAL COMPRESSION OF SAID REFRIGERANT PORTION, PASSING SAID EXPANDED AND COOLED REFRIGERANT PORTION TO A SEC- 